Boiler



Oct. 20,1936. H. B. SMITH 2,058,043

BOILER Filed April 27, 1931 2 Sheets-Sheet 1 I\ INVENTORI J/epman 5. Smith EB RW ATTORNEY Patented Oct. 20, 1936 PATENT OFFICE BOILER Herman B. Smith, Plainfield, N. .lL, assignor'to The Babcock & Wilcox Company, Bayonne, N. J., a corporation of New Jersey 4 Application April 27, 1931, Serial No. 533,067

3 Claims.

This invention relates to boilers associated with a furnace and more particularly to boilers wherein material containing a high content of noncombustible matter is utilized as a fuel.

- In many industrial processes combustible materials are produced thatare burned to produce 7 some desirable by-product, and this invention contemplates a boiler associated with a furnace especially designed to utilize the heat of combustion of a product such as the black liquor which comes from digesting vats of a wood pulp fibre plant, and is processed by burning.

The boiler and furnace contemplated in this invention are also useful in burning other fuels,

and an effective furnace temperature control is provided as a part of this invention, to aid in the successful combustion of fuels that are difficult to burn.' For example, when fuel which has a high aqueous content is used it mustbe dried before effective combustion takes place, hence, when such fuel is to be burned the furnace walls and roof should be cooled to a lesser degree than when a dry fuel, such as pulverized coal, is used. In connection with the use of wet fuel, it is extremely desirable to locate the fuel inlet at the topof the furnace setting, so that the fuel may be projected through combustion gases at, high temperatures and hence more quickly dried.

An object of the invention is to provide a boiler associated with a furnace, wherein a fuel is used that has a high content of non-combustible ma terial. U

A specific object of the invention is to provide a boiler associated with a furnace wherein the black liquor from digesting vats in wood pulp plants is utilized as a fuel to be burned in the furnace, and especially contemplates a boiler structure suitable for this purpose.

Further objects will be apparent to those skilled in this particular art from the claims and the description in the specification in connection with the drawings, in which Fig. 1 is a sectional side view of a boiler and a furnace forming an illustrative embodiment o the invention, and

Fig. 2 is a sectional plan view taken along the line 22 of Fig. 1.

In the embodiment ofthe invention which has been chosen for purposes of illustration, a combustion chamber I is provided that is especially adapted to .burn a fuel .which has a high con tent of non-combustible material. In the lower part of the combustion chamber is provided a tap 2 for the removal of the unburned portion of the fuel, which, when the fuel is black liquor from a wood pulp fibre process, is termed smelt, and is removed for further treatment for obtaining val.- uable by-products therefrom.

Above the tap 2 are inlets 3 which may be arranged in rows, through which a processing ma- I other end to a header 1.

terial may be admitted to mix with the liquor to be burned for the purpose of promoting desirable chemical reactions and through which air may be directed against the material to promote combustion. Another inlet 4 is provided in the upper portion of the furnace to admit the liquor which is tobe processed and burned.

At the top of the combustion chamber is a row of roof tubes 5 connected atone end to and supported by a steam and water drum 6 and at its The ends of the tubes adjacent the header 1 rest upon a portion of the furnace setting and are supported thereby free to expand. This row of tubes 5, in addition to tue of the heat absorbing medium which is circulated through them keeps the roof cool, and at the same time acts as.-'a partial support for the roof, hence providing a simple and cheap roof construction. ,In addition, they serve to aid in the control of the furnace temperature.

As best shown in Fig. 2, header 1 is supplied with water from a drum 6 by feed pipes 23which are connected to the header 7 at each end thereof. Water from the drum flows through the downcomers to the headers 24', and then through pipes 23 to the header 1. The waterand any steam that is generated then flows up'the tubes to the drum 6 to complete a steam and water circulatory system.

Disposed beyond a refractory structure 0, which forms a partition that partially separates the combustion chamber from the boiler gas pass, is a boiler of the Stirling type, which, in this instance comprises a pair of upper drums 6 and 9 connected together by steam circulators l0 and water circulators II, and which are further connected together by banks of tubes l2 and i3, through a lower drum I l.

The partition 8 shields-the lower portion of the furnace from the cooling effect of the steam generating tubes, andthus aids in the combustion of the liquid fuel. At the sametime the partition 8 concentrates the direct heat of combustion from the burning fuel against the roof and so necessitates the provision of a protective device such as the roof tubes previously described, to prevent destruction of the roof structure. This is especially true when'black liquor is burned, for hot combustion gases from such a fuel have a destructive effect on furnace brick work. The partition 8 is also hollow, so that air may be circulated through it to aid in the control'of the furnac; temperature.

The front row of tubes [5 of the bank i2 is more widely spacedthan the other tubes of the bank as best shown in Fig. 2, and acts as a slag screen for the rest of the tubes; and disposed below these tubes is a pit l6 especially adapted to receive slag and ash checked by the tubes I 5. An opening I! is provided in the pit to readily provide for the removal of this slag and ash. The tubes I5 are vertically inclined so that the molten solids checked thereby drop into the hopper l6 and radiate back heat.

A row of tubes making up a superheater 20 is connected at one end directly to the steam space of the drum 9, and is curved .to extend downward parallel to the tubes of the bank l3 for the greater portion of its length in a hairpin bend.

The other end of the row of tubes of this superheater is secured to an outlet header 2| disposed between the drums 8 and 9. The header 2i is shielded from contact with combustion gases by a roof bafile member 22. f

The superheater as just described is especially desirable in a boiler-furnace organization such as the one herein described, for in addition to the elimination of an inlet header the tubes are so disposed with respect to the flow of combustion gases during the operation of the device that while presenting an adequate superheating heat transfer surface to the sweep of gases, they present a minimum'suriace upon which soot, ash, and slag will be deposited.

In the operation of the device when black liquor is used as a fuel, in starting, a fire is built in the lower portion of the furnace i to heat the floor and side walls. When this heating has been accomplished normal operation is ready to be started. The black liquor is admitted to the combustion chamber by means of the inlet 4 and is ignited by the fire. From this time on combustion continues as long as black liquor is supplied. While this combustion is taking place an.

additional chemical reaction is transpiring in the unburned molten mass at the bottom of combus- I combustible material is separated from the combustion gases and is projected to the bottom of the combustion chamber. The unburned combustible matter so projected joins the molten mass of materialv being processed and is burned.

Combustion gases from this operation strike the cool roof tubes and are deflected through the several gas passes as indicated by arrows. The first gas pass is downward to augment the removal of solids. The hopper I6 is also a reversing chamber, so that a' portion of the. solids that might ordinarily not be removed from the furnace gases by the slag screen tubes ii, are removed by the reversing action of the gases. The freezing solids are allowed to accumulate in the hopper and they radiate heat to the steam generating tubes as they cool, so that part of the heat which generates steam is salvaged from cooling solids.

When the gases strike the row of tubes I, which as aforesaid act as a slag screen for the other tubes, much of the remaining ash and other non-combustible material that is swept along by the combustion gases cool and drop to the bottom of the pit l6 so that the gases of combustion that sweep successively along the tubes of the banks l2 and I3 and across the tubes of the superheater 2!! in gas passes defined by the bailies 30,

-are comparatively free from solid non-combustible material. After sweeping along the tubes in the rear of bank i3 the combustion gases flow through a suitable gas outlet 3|.

A boiler associated with a furnace has been described in some detail as utilizing the black liquor from digesting vats of a wood pulp fibre plant as a fuel, but obviously the device shown and described is especially adapted for use with any fuel which has a high content of non-combustible material, and although a specific structure has been described in some detail, it is to be understood that changes, additions, substitutions and omissions may be made therein within the spirit of the invention as defined by the appended claims.

I claim:

1. In a steam boiler associated with a furnace having an inclined roof, an upper drum, a lower drum connected thereto by steam generating tubes arranged to form a primary steam and water circulatory system, a row of radiantly heated riser tubes disposed along the furnace roof and connected at one end to said upper drum and at the other end to a header, and conduit members independent of said steam generating tubes joining said header with said upper drum to form a secondary steam and water circulatory system, said conduit members being connected to said upper drum mainly below the level of the connections of said roof tubes to said drum.

2. In a steam boiler associated with a furnace having an inclined roof, an upper drum, a lower drum connected thereto by steam generating tubes arranged to form a primary steam and water circulatory system, a row of radiantly heated riser tubes disposed along the furnace roof and connected at one end to said upper drumand at theother end to a header, and conduit members independent of said steam generating tubes joining said header with said upper drum to form a secondary steam and water, circulatory system, said conduit members including a group of downcomer tubes connected to said upper drum in a circumferential row mainly below the level of the connections of said-roof tubes to said drum. 3. In a steam boiler associated with a furnace having an inclined roof, an upper drum, a lower drum connected theretoby steam generating tubes arranged to form a primary steam and water circulatory system, a row of radiantly heated riser tubesdisposed along the furnace roof and connected at one end to said upper drum and at the other end to a header, and external conduit members independent of said steam generating tubes joining the opposite ends of said header with the corresponding ends of said upper drum to form a secondary steam and water circulatory system, said'conduit members including a group of downcomer tubes connected to said upper drum in a circumferential row mainly below the level'of the connections of said roof tubes to said drum.

, HERMAN B. SMITH. 

